Guaiane sesquiterpene lactones and, amino acid-sesquiterpene lactone conjugates from the aerial parts of Saussurea pulchella

Abstract

Two new guaiane sesquiterpene lactones (1 and 2) and seven new amino acid-sesquiterpene lactone conjugates (3-9), together with six known sesquiterpene lactones (10-15), were isolated from the methanol extract of the aerial parts of Saussurea pulchella. Their structures were determined on the basis of spectroscopic and chemical methods to be 8 alpha-O-(3'-hydroxy-3'-methylbutyryl)desacylcynaropicrin (1), 8 alpha-O-(2', 3'-dihydroxyisobutyryl)11 beta,13-dihydrodesacylcynaropicrin (2), and pulchellamines A, B, C, D, E, F, and G (3-9). The structures of the new amino acid-sesquiterpene lactone conjugates, pulchellamines A, B, C, D, E, F, and G (3-9), were confirmed by synthesis. The isolated compounds were evaluated for cytotoxic activity against four human tumor cell lines. Compounds 11 and 12 exhibited cytotoxicity against skin melanoma (SK-MEL-2) and ovary malignant ascites (SK-OV-3) human tumor cell lines with ED(50) values of 1.53 and 4.07 mu M, and 2.49 and 7.42 mu M, respectively.